Comparison of normal types, appropriate mutants, and phenocopies of two species of Neurospora, N. crassa and N. tetrasperma, will be used for analysis of the development of the sexual reproductive apparatus. The main foci will be on (a) membrane systems involved in spore excision and (b) a perithecial protein that appears at fertilization and rapidly increases in quantity until it occurs at 50 to 60 percent of the total soluble protein in the system. Electron microscopy will be used to observe membrane systems that partition cytoplasm and nuclei in the normal process of spore excision but behave aberrantly in mutants where excision does not occur. The perithecial protein will be further characterized, and its site of occurrence within perithecia will be studied by means of fluorescein-tagged antibody against the protein. The objectives of the work are to define and establish interrelationships among the genetically determined components of the developmental system. BIBLIOGRAPHIC REFERENCES: Srb, Adrian M., Mutation and selection in fungi. in Haploids in Higher Plants: Advances and Potential. Proceedings of the 1st International Symposium. K.J. Kasha, editor. pp. 289-307. 1974. Srb, Adrian M., Emerson, Rollins Adams. Dictionary of American Biography, Supplement 4, 1946-1950. pp. 252-253. Charles Scribners Sons, N.Y. 1974.